Process for production of polyarylenes

ABSTRACT

Polyarylenes, polymers of aromatic hydrocarbons, are obtained by the coupling of aromatic hydrocarbons over a high surface area active carbon.

United States Patent 191 [111 3,855,332 Wang Dec. 17, 1974 PROCESS FOR.PRODUCTION OF [56] References Cited POLYARYLENES I UNITED STATES PATENTSI [75] Inventor: Chen-Shen Wang, Naperville, Ill. 3,437,695 4/1969 Kruse260/2 H 3,729,433 4/1973 Billow et al 260/2 H [73] Asslgnee StandardCompzmy, Chlcago, 3,734,866 5/1973 Aylies et a]. 260/2-H 22 Filed: Dec.12, 1972 Primary Examiner-Curtis R. Davis [21] Appl 314424 Attorney,Agent, or FirmRalph C. Medhurst; Arthur Related U.S. ApplicationData G.Gilkes; William T. McClain V [63] Continuation-impart of Ser. No.169,367, Aug. 5,

1971, abandoned. [57] ABSTRACT Polyarylenes, polymers of aromatichydrocarbons, are [52] U.S. Cl 260/670, 26 O/2 H, 260/668 R Obtained bythe coupling ofwaromatic hydrocarbons Int. Cl. C07C 15/12 Over a iSurface area active carbon 7 Field of Search 260/2 H, 668 R, 670

12 Claims, 1 Drawing Figure TIME, Hours PATENTEDBEE171974 3.855.332

TIME, Hours INVENTOR.

Chen .Shen Wang BY PROCESS FOR PRODUCTION OF POLYARYLENESCROSS-REFERENCE This application is a continuation-in-part of Ser. No.169,367, filed Aug. 5, l97l and now abandoned on behalf of the sameinventor.

INTRODUCTION Over the past decade there has been a growing need for hightemperature stable polymers. The high degree of thermal stabilityassociated with the arylene bond in polyarylenes has been known for sometime. .The linear polyarylenes produced to date have generally been oflittle utility due to their relative insolubility and infusibility.Wennerberg has disclosed a process for making polyarylenes which arerelatively soluble, fusible, and thermally stable in his co-pendingapplication, Ser. No. 264.846, filed'Ju ne 21, 1972 as acontinuation-in-part of Ser. No. 858,867, filed Sept. 17, 1969 nowabandoned. These branched polyphenylenes are particularly useful in hightemperature applications such as carbon fiber composites and ablativematerials.

Low molecular weight polyarylenes are useful in the preparation ofablative materials and in the preparation of phosphonylatedpolyarylenes. These phosphonylated polyarylenes were disclosed in mycopending application, Ser. No. 169,430, filed Aug. 5, 1971 and nowabandoned. These phosphonylated polyarylenes are useful, as flameretardants for cellular polymers and thermoplastics.

SUMMARY OF THE INVENTION This invention relates to an improved processfor making fusible, soluble, and thermally stable branched polyarylenesof low molecular weight. This improved DESCRIPTION OF THE INVENTION FIG.I is a plot generally showing the temperaturetime characteristics of thereaction taking place in the process of this invention.

This invention is directed to an improved process for making branchedpolyarylenes having a low inherent viscosity. By low inherent viscosity,I mean'aninherent viscosity not greater than about 0.065 when measuredin trichlorobenzene at 135C at a concentration of 0.02 g/ml. Preferably.thev inherent viscosity is between about 0.025 and 0.045. This preferredrange roughly corresponds to a number average molecular weight range ofabout .1000 to about 2000.

The process of this invention involves the contacting of aromatichydrocarbons with a high surface area ac.- tive carbon catalyst systemin the presence of hydrogen at a temperature of at least about 800F andat elevated pressures. In general, the pressures should be at'leastabout 600 psig. The hydrogen partial pressure should be at least about10% of the total pressure at reaction conditions. The surface area ofthe active carbon catalyst is at least about 1500 m /g.

These polyarylenes are readily prepared by a onestep process startingwith partially'hydrogenated aromatic hydrocarbons, by a two-step processstarting with non-hydrogenated aromatic hydrocarbons or a mixture ofnon-hydrogenated aromatic and partially hydrogenated aromatichydrocarbons, Or by a combination of these processes. The one-stepprocess consists of the catalytic dehydrogenative coupling of thepartially hydrogenated aromatic hydrocarbons in the presence of hydrogenat elevated temperatures and pressures. The

two-step process consists of a controlled partial hydrogenation as wellas the dehydrogenative coupling. The two step process begins with eithernon-hydrogenated aromatic hydrocarbons or a mixture of nonhydrogenatedaromatic hydrocarbons and partially hydrogenated aromatic hydrocarbons.Preferably, a mixture of non-hydrogenated aromatics with from about 1%to 10% of partially hydrogenated aromatics is employed. This two-stepprocess of controlled hydrogenation and dehydrogenative couplingcan berun as two separate steps or is preferably combined into one processduring which the controlled hydrogenation and the dehydrogenativecoupling can be occurring simultaneously.

The polyarylenes produced by the process of this invention arecompositions whch retain a high degree of 0 thermal stability. whilepossessing solubility invarious aromatic solvents. The polyarylenes canbe dissolved to different extents, depending on their molecular weightand structure, in solvents such as benzene, naphthalene, bromobenzene,and chlorobenzene. The halogenated aromatics are the preferred solvents.

The polymers produced by this invention are particularly useful inapplications requiringhigh-temperature resistance. Among theapplications for this polymer are use in carbon fiber composites, inablative materials,

and in the preparation of phosphonylated polyarylenes.

The high surface area active carbon used in this invention has a surfacearea of at least about 1500 m lg. Preferably, the surface area isbetween 2000 m /g and 3500 m /g.

The active carbon catalyst can also have other active ingredientsincorporated into it. Preferably, the active carbon catalyst is basetreated. Thebase treatmentof the carbon catalyst involves contacting theactive carbon catalyst with a base material prior to its use in theprocess of this invention. Typical bases which may be used are KOI-I,NaOH, Ca(OH) Mg(Ol-I) and the like. The preferred bases are NaOI-I andKOH.

If the carbon catalyst of this invention is base treated, it is usuallysaturated with the base material. Saturation is herein defined to mean abase loading of the carbon catalyst in the range of about 10% to about15% by weight of the total catalyst weight. Saturation is achieved bymixing a properly concentrated volume of base solution with the carboncatalyst. The volume of base solution should be approximately equal tothe pore volume of the carbon catalyst. After base treatment, thecatalyst is heated at about '-l 00 C for 24-48 hours in order to removethe water from the cat alyst and to ensure an even distribution of thebase material.

If the carbon catalyst is supersaturated with base material so that thebase content is greater than about by weight, longer reaction times arerequired and polyarylenes. of very low molecular weights are produced.

The amount of catalyst necessary to effectively be utilized in theprocess of this invention will vary with the reaction system beingpolymerized and the reaction conditions in terms of time, temperatureand pressure. If an insufficient amount of catalyst is used for aparticular reaction system under any set of reaction conditions,reaction rates will be decreased. If excess catalyst is used, conversionwill usually be decreased and coke formation will occur. For mostreaction systems, at least about 1% by weight catalyst, based on themonomer weight, is used and preferably about 2% to about 4% by weight.

The aromatic hydrocarbons which are polymerized in the process of thisinventionare defined to be any compound containing an aromatic ringstructure which is either substituted or non-substituted. If it issubstituted, the substituted aromatic compounds cannot have groups whichare too large and preferably such compounds are mono-, diandtri-substituted benzene ring compounds wherein the substituents arealkyl groups containing 1 to 3 carbon atoms.

Included within the class of aromatic hydrocarbons are partiallyhydrogenated aromatic hydrocarbons as distinguished fromnon-hydrogenated aromatic hydrocarbons which are also in the class. Suchpartially hydrogenated aromatic hydrocarbons must be hydrogenated to atleast their dihydro derivative-but must not be fully hydrogenated. Thenon-hydrogenated aromatic and the partially hydrogenated aromatichydrocarbons may be reacted alone or in combination. Preferably, thenon-hydrogenated aromatic hydrocarbons are reacted in the presence of atleast about 1% to 10%, pref erably about 2% to about 5%, by weight ofthe partially hydrogenated aromatics as based on their total com-- binedweight.

Specific examples of non-hydrogenated aromatic hydrocarbons which can bepolymerized by the process of this invention are compounds that have anaromatic ring structure such as phenyl, biphenyl, toluene, xylenes,ethylbenzene, naphthalene, mesitylene, anthracene and the like.

The partially hydrogenated aromatic hydrocarbons which can be utilizedin the process of this invention are generally partially hydrogenatedderivatives of the non-hydrogenated aromatic hydrocarbons listed above.Specific examples of partially hydrogenated aromatics are thehydrophenyls such as cyclohexadiene and cyclohexene, the hydrobiphenylssuch as phenyl cyclohexadiene, phenyl cyclohexene, and phenylcyclohexane, the hydrotoluenes, the hydroxylenes, the hydronaphthalenes.the hydroanthracenes, and the like.

All ofthe aromatic hydrocarbons which are polymerized' in the process ofthis invention must have at least two unsubstituted positions for thecoupling reactions.

The polymerization must be conducted in the presence of hydrogen. Thehydrogen partial pressure should be at least about 10% of the totalpressure at reaction conditions. Preferably the hydrogen partialpressure is from about 30 to 60% of the total reaction pressure atreaction conditions. More preferable, the partial hydrogen pressure isabout half of the total pressure. In general, if the process of thisinvention is carried out in an autoclave reactor, the initial charge ofhydrogen gas at room temperature should be at least about 50 psig andpreferably between about 200 psig and 400 psig.

The presence of an inert solvent is not necessary. However, with somemonomers it may be desirable to conduct the reaction in a hydrocarbonsolvent which tends to remain relatively inert under the conditions ofthe reaction.

Specific time, pressure and temperature conditions for the process ofthis invention cannot be given since such will depend upon the nature ofthe particular aromatic hydrocarbon being polymerized. For example,condensed ring compounds such as naphthalene are in general morereactive than single ring compounds such as biphenyl and the reactionsmay be carried out under milder conditions with the former.

However, time and temperature conditions for a.

batch process beginning with non-hydrogenated aromatic hydrocarbons or amixture of non-hydrogenated and partially-hydrogenated aromatichydrocarbons can be taught generally by referring to reactiontemperature reaction time relationships for any particular reactingsystem being subjected to a constant heat input.

The polyarylenes produced by the process of this invention are believedto be produced by the dehydrogenative coupling of partially hydrogenatedaromatic hydrocarbons. Therefore, if partially hydrogenated aromatichydrocarbons are not initially used as monomer reactants, the couplingcannot effectively take place until the aromatic hydrocarbons arepartially hydrogenated. Hydrogenation must produce at least dihydroderivatives but must not result in complete hydrogenation. The partialhydrogenation of the aromatic hydrocarbons in the process of thisinvention is exothermic the dehydrogenative coupling of the partiallyhydrogenated aromatics is endothermic. Utilizing these characteristicsunder conditions of constant heat input to the reaction system, reactiontimes and temperatures may be generally identified.

In order to illustrate this point, reference is made to FIG. 1 where ageneral reaction temperature vs. reaction time curve is given for anaromatic hydrocarbon reaction system having a constant heat input andwhich is polymerized in accordance with the process of this invention.With the constant heat input, the reaction system is preheated for aperiod of time a, to a temperature a,,. This preheat period extends upto a point A on the curve. Point A is approximately on that portion ofthe curve where the slope changes from steep to gradual. After preheat,the reaction system begins to react in substantial proportions in termsof partial hydrogenation with some coupling up to the peak point Bhaving corresponding time and temperature coordinates of b, and b,,. Itis from this point that it is thought that the major dehydrogenativecoupling occurs to form the polyarylene, although some partialhydrogenation is still most likely occurring. Thedehydrogenativecoupling is considered for all practicalpu'rposes completed at point Cwhere the curve starts to level off. It is therefor at point C withcorresponding time and temperature coordinates of c, and c that thereaction is terminated by terminating heat input to the reaction andallowing the reaction system to go to room temperature. Therefore,relative to this general curve, reaction-time is considered to be thatinterval of time betemperature and preheat completion, i.e., between band a,,.

As previously stated, the reaction time and reaction temperaturecorrelations for the process of this invention will vary from system tosystem. However, for a batch 'process beginning with non-hydrogenatedaromatic hydrocarbons or a mixture of non-hydrogenated andpartially-hydrogenated aromatic hydrocarbons, the

heat-up period corresponding to a, hours on the plot of FIG. 1 willtypically vary from about 0.5 to about 2 hours. Similarly, the heat-uptemperatures corresponding to a on the curve can be from about 800 toabout 1000F. The peak reaction temperatures, b corresponding to point Bcan be about 900 to about 1300F, preferably I000F to l200F. The reactiontemperature, c,,, at which the reaction is terminated is about 800 toabout I000F. Therefore, the overall reaction temperature interval of bto a can have reaction temperatures varying from about 800F to about1300F. The reaction time, i.e., the period of time between a,

and c, is from about 2 to about 9 hours.

we have found temperatures within the range of 800F to I300F, preferably900F to l200F, and pressures within the range of 600 psig to 2000 psig,preferably I000 psig to I700 psig, to be particularly useful.

The following examples are provided to better illustrate the process ofthis invention.

EXAMPLE I Into a stirred 300 ml autoclave there was charged 2.0

g of an active carbon catalyst having a surface area of about 3000 m /g,97.5 g of'biphenyl, 2.5 g of phenyl cyclohexane, and 300 psig ofhydrogen gas. Constant heat input conditions were applied. The initialreaction temperature, a of FIG. 1', was about 900F. The peak reactiontemperature was 1095Fand the maximum reaction pressure was 1700 psig.The final reaction temperature was 940F. The reaction time includingheat-up was 7 hours. No coke was produced by the reaction.

After the polymerization was concluded, the total crude product wasdissolved in trichlorobenzene. The conversion to polymer soluble intrichlorobenzene was 18.5%. The inherent viscosity of the solubleproduct was 0.03 when measured in trichlorobenzene at 135C. Thiscorresponds to a number average molecular weight of about 1200. SeeTable l.

TABLE I Peak Maximum Final- Time 7a A proximate Reaction I ReactionReaction (incl. Conversion 1 N3. Average Ex. Temperature, Pressure,Temperature, heat-up) to Soluble Inherent Molecular No. Catalyst F psigF I hrs. Polyarylene Viscosity Weight I Active Carbon"" I095 I700 940 718.5 0.03 1200 II .l4 /r KOH on Active Carbon" I085 I450 975 7 26.90.03- 1200 III I4 KOH on I Active Carbon"" I055 I245 985 7 24.0 0.03I200 IV MoO on Active Carbon I I00+ I530 I095 4%: 18.0 3500 'Activecarbon had a surface area of 3000 nf-lg.

""Mcasurcd at 135C in trichlorohenzene usinga'Cannon-Ubbelohdcviscometer.

generally within the range of 600 psig to 1200 psig, al-

though higher pressures are possible. The maximumpressure is generallywithin the range of I000 psig to 2000 psig, preferably I200 psig to 1700psig.

We have also ascertained advantageous reaction conditions for theone-step'process beginning with partially hydrogenated aromatichydrocarbons and for the twostep process beginning with non-hydrogenatedaromatic hydrocarbons or a mixture of non-hydrogenated aromatichydrocarbons and matic hydrocarbons.

In a one-step process startin drogenated aromatic hydrocarbons,temperatures within the range of 800F to about 1300F, preferably about900F to l200F, and pressures within the range of 600 psig to 2000 psig,preferably 1000 psig to 1700 psig, more preferably 1200 psig to 1600psig, have been found useful.

In a two-step process starting with non-hydrogenated aromatichydrocarbons or a mixture of nonhydrogenated and partially-hydrogenatedaromatic hydrocarbons, we have found that temperatures within the rangeof 400F to l200F, preferably 800F to I I00F, and'pressures within therange of500 psig to 2000 psig, preferably 800 psig to I500 psig, areuseful in the hydrogenation step; In the dehydrogenation step,

EXAMPLES lI-lV the same manner as Example I. The active carbon catalystwas modified as indicated in Table I. The reaction conditions andresults are also shown in Table l.

While this invention has been described in conjunc- -tion with certainspecific embodiments, it is evident that many alternatives,modifications, and variations partially hydrogenated, arog with thepartially hy- I will be apparent to those skilled in the art.Accordingly, the appended claims are intended to embrace all modifications, alternatives, and variations that come within the spirit andscope of thisinvention.

What I claim is:

l. A process for the preparation of branched polyary- Y lenes whichcomprises treating an aromatic hydrocarbon, a partially hydrogenatedaromatic hydrocarbon, or a mixture of an aromatic hydrocarbon and apartially hydrogenated aromatic hydrocarbon. with an active carbon whosesurface'area is at least about 1500 m /g in the prese least 800F.

2. The process of claim 1 wherein thetemperature is between 800F and l300Fand the pressure is between 600 psig and 2000 psig.

3. The process of claim 2 wherein the surface area of the active carbonis between 2000m /g and 3500 m /g.'

nce of hydrogen and at a temperature of at 4. The process of claim 2wherein the active carbon catalyst is loaded with from about 10% toabout by weight of base material.

5. The process of claim 4 wherein the base material is selected from thegroup consisting of KOH, NaOl-l, Ca(0H)2, and

6. The process of claim 1 wherein the partially hydrogenated aromatichydrocarbon is a member of the group consisting of a partiallyhydrogenated benzene, a partially hydrogenated biphenyl, a partiallyhydrogenated toluene, a partially hydrogenated naphthalene, andalkylated hydrocarbon derivatives thereof.

7. The process of claim 1 wherein the aromatic hydrocarbon is selectedfrom the group consisting of henzene, biphenyl, toluene, xylene,ethylbenzene, and

catalyst is from 1 to 4% of the weight of the reactants. l l

1. A PROCESS FOR THE PREPARATION OF BRANCHED POLYARYLENES WHICHCOMPRISES TREATING AN AROMATIC HYDROCARBON, A PARTIALLY HYDROGENATEDAROMATIC HYDROCARBON, OR A MIXTURE OF AN AROMATIC HYDROCARBON AND APARTIALLY HYDROGENATED AROMATIC HYDROCARBON WITH AN ACTIVE CARBON WHOSESURFACE AREA IS AT LEAST ABOUT 1500 M2/G IN THE PRESENCE OF HYDROGEN ANDAT A TEMPERATURE OF AT LEAST 800*F.
 2. The process of claim 1 whereinthe temperature is between 800*F and 1300*F and the pressure is between600 psig and 2000 psig.
 3. The process of claim 2 wherein the surfacearea of the active carbon is between 2000 m2/g and 3500 m2/g.
 4. Theprocess of claim 2 wherein the active carbon catalyst is loaded withfrom about 10% to about 15% by weight of base material.
 5. The processof claim 4 wherein the base material is selected from the groupconsisting of KOH, NaOH, Ca(OH)2, and Mg(OH)2.
 6. The process of claim 1wherein the partially hydrogenated aromatic hydrocarbon is a member ofthe group consisting of a partially hydrogenated benzene, a partiallyhydrogenated biphenyl, a partially hydrogenated toluene, a partiallyhydrogenated naphthalene, and alkylated hydrocarbon derivatives thereof.7. The process of claim 1 wherein the aromatic hydrocarbon is selectedfrom the group consisting of benzene, biphenyl, toluene, xylene,ethylbenzene, and naphthalene.
 8. The process of claim 1 wherein thearomatic hydrocarbon is biphenyl.
 9. The process of claim 1 wherein thearomatic hydrocarbon is biphenyl and the partially hydrogenated aromatichydrocarbon is phenyl cyclohexane.
 10. The process of claim 1 whereinthe partially hydrogenated aromatic hydrocarbon is from 2 to 5% of thetotal weight of reactants.
 11. The process of claim 1 wherein thepartial hydrogen pressure under reaction conditions is at least 30% ofthe total reaction pressure.
 12. The process of claim 1 wherein theactive carbon catalyst is from 1 to 4% of the weight of the reactants.